Wheelchair cushion to transfer heat and moisture

ABSTRACT

A cushion adapted to reduce heat and moisture from a wheelchair user&#39;s body, including a cushion member having a compressible material that permits air and moisture to flow through the cushion member. The cushion also includes an air and water permeable cover adapted to receive the cushion member. The cover includes an interface member having an outer layer formed of a hydrophobic material, an inner layer formed of a hydrophilic material, and a spacer layer having fibers positioned between, and generally perpendicular to, the outer and inner layers.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 60/559,592, filed Apr. 5, 2004 and entitled Wheelchair Cushion to Transfer Heat and Moisture, which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION

This invention relates to wheelchair cushions, particularly cushions that provide for improved heat and moisture transfer from the person in the wheelchair.

BACKGROUND OF THE INVENTION

It is well known that the skin of people who are confined to wheelchairs is vulnerable to potentially injurious consequences resulting from the long periods of time that they sit in their wheelchairs. Specifically, sitting in the same position for long periods of time subjects portions of a person's body to pressures, increased temperatures and moisture resulting from perspiration. Heat and moisture are thought to be significant factors in skin tissue stress and breakdown. The relative contribution of these factors as causative agents for pressure sores is not fully understood. However, it has been shown that moisture is the greatest influence in the formation of superficial pressure sores. Such conditions can combine to compromise the integrity of a person's skin, potentially resulting in irritation, decubitis ulcers (commonly known as bedsores), and other dermal ulcers. Left untreated, nearby tissue begins to die, eventually resulting in an ulcer that can reach a person's bone, leaving an open cavity with resulting secondary infections that can cause serious illnesses or even death.

It is not unusual for a person confined to a wheelchair to spend up to 14 to 16 hours a day sitting in their chair. Depending upon a person's capacity for movement, several portions of a person's body, including the back, forearms, and head may be in contact with the wheelchair for most or all of that time every day. Typically, those parts of the body that are exposed to long term contact with the chair are rested on a cushion of some sort to reduce and distribute the pressure to which the skin is subjected. While a cushion may be an effective way to reduce and more uniformly distribute skin pressure, a cushion may do very little to remove heat or moisture. Therefore, these parts of the body are still potentially vulnerable to a reduction in skin integrity, unless heat and moisture can be effectively removed from the person's skin.

Some attempts have been made to relieve the harmful high temperature and moisture conditions on people's skin. For example, Sunrise Medical sells a seat back with a cushioning pad that includes a spacer fabric that covers a foam pad to allow air flow around their foam pad. What is needed, however, is a cushioning device that uses substantially the entire cushion to help draw moisture and heat away from the wheelchair user's body parts that are in contact with the wheelchair as well as distribute pressures more evenly across the user's body. Such an invention would reduce the risk of such injuries as decubitis ulcers.

SUMMARY OF THE INVENTION

The present invention is directed to a cushion adapted to reduce heat and moisture from a wheelchair user's body. The cushion includes a cushion member with a compressible material that permits air and moisture to flow through it and an air and water permeable cover adapted to receive the cushion member. The cover includes an interface member having an outer layer, an inner layer positioned substantially parallel to the outer layer, and a spacer layer positioned therebetween. The outer layer includes a hydrophobic material, the inner layer includes a hydrophilic material, and the spacer layer includes a compressible hydrophobic material that has fibers positioned between, and generally perpendicular to, the outer and inner layers. The cushion can be configured to interface with any one of the wheelchair user's back, arm, head, and leg.

The current invention is also directed to a method for reducing heat and moisture from a body surface of a wheelchair user seated in a wheelchair. The method includes the steps of providing an air and moisture permeable cushion that includes a cushion member having a compressible material and a cover adapted to receive the cushion member and engage a portion of the wheelchair user's body, such as the back, head, arm or leg. The cushion is then positioned between the portion of the wheelchair user's body and the wheelchair. The cover includes an outer layer formed of a hydrophobic material, an inner layer formed of a hydrophilic material and positioned substantially parallel to the outer layer, and a spacer layer constructed of a compressible hydrophobic material and having fibers positioned between, and generally perpendicular to, the outer and inner layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a wheelchair that includes cushions in accordance with an embodiment of the invention.

FIG. 2 is an isometric view of a back rest cushion in accordance with one embodiment of the invention.

FIG. 3 is a cutaway view, showing the layers of material included, of the back rest cushion shown in FIG. 2.

FIG. 4 is back view of a cushion member of the back rest cushion showing an alternative support member.

FIG. 5 is an isometric view of a cushion member in accordance with one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a wheelchair 10 typically includes a frame 12, which provides the primary structure and support for the wheelchair 10. Wheelchair 10 has a primary wheel 14 located on each of an opposing left side 11 and right side 13 of wheelchair 10. Each primary wheel 14 is fixed to the frame 12 at a center point of primary wheel 14 towards a back side 17 of the wheelchair 10. Primary wheels 14 can be rotated about an axle to propel the wheelchair 10 in either a fore or aft direction by the application of an external force, from a wheelchair user or another person or, alternatively, with the use of a mechanized drive system. In addition, wheelchair 10 may include a caster wheel 16, coupled to frame 12 of each of the left side 11 and right side 13 and towards the bottom of a front side 19 of wheelchair 10. The caster wheels 16 are significantly smaller than the primary wheels 14 and are used primarily to facilitate steering and movement of the wheelchair 10 and contribute to the stability of the wheelchair 10 while the wheelchair is moving or at rest.

Wheelchair 10 has a seat 20 and a backrest 22 coupled or integrated to frame 12, which substantially form a chair to accept and support a portion of the wheelchair user's torso and legs while the user is sitting in wheelchair 10. In addition, wheelchair 10 may have at least one foot rest 24, at least one arm rest 26, and a head rest 28, all coupled to or integrated with frame 12, designed to accept and support the user's feet and lower legs, arms, and head, respectively. The wheelchair 10 could have a number of other features, such as a self-contained propulsion system, including those that have electric motors coupled to drive systems; various frame structures, including variations on the foot, arm, and head rests; different wheel configurations, including variations in the size, type and number of wheels; and other optional accessories or combinations of accessories (none of which are shown).

The wheelchair 10 may include a back rest cushion 30, attached or positioned on a front side of back rest 22, an arm rest cushion 32, attached or positioned on a top side of each arm rest 26, and a head rest cushion 34, attached or positioned on a front side of head rest 28. It is to be understood that while one embodiment includes back rest cushion 30, two arm rest cushions 32 and head rest cushion 34, any combination of cushions can be used without departing from the scope of the invention. For example, one particular wheelchair user may require only a back rest cushion 30; another user may require a back rest cushion 30 and either one or two arm rest cushions 32; still another user may require a back rest cushion 30 and a head rest cushion 34. It is to be further understood that a particular user may require or desire to have a cushion for other portions of the body, including, for example, cushions for a portion of the user's legs.

The back rest cushion 30 is positioned between the back rest 22 and the user when the user is sitting in the wheelchair 10, so that the front surface 31 is positioned closer to the wheelchair user's back than the back surface 33. Back rest 22 is shaped to accept a portion of a human torso. The back rest 22 may have one or more openings of any size and shape along the back rest 22. Back rest 22, in one embodiment, is made out of a hard polymeric material, but any suitable material may be used, including materials such as leather, synthetic leathers, metallic or composite materials, or fabrics. It is to be understood that back rest 22 may be made of many different materials and be of different sizes and shapes.

Referring to FIGS. 2 and 3, the cushion 30 has a front surface 31 and an opposing back surface 33, which together include the majority of the surface area of back rest cushion 30. Cushion 30 has a thickness 32 defined as the distance between the front surface 31 and the back surface 33. The thickness 32 of back rest cushion 30 may or may not be uniform across the front surface 31. Cushion 30 may include a edge surface 35, which is located between the front 31 and back 33 surfaces along the perimeters of those surfaces 31, 33. The cushion 30 may be shaped and sized so that, when it is located on a front side of back rest 22, it covers approximately the entire front side of the back rest 22. The actual shape and size of the cushion 30 may vary depending upon the type of wheelchair or other factors. For example, the cushion 30 could actually be made of more than one similarly constructed cushions positioned in front of back rest 22, which may or may not be connected to or adjacent each other. Alternatively, the back rest cushion 30 may be sized to cover only a portion of the front of back rest 22.

The cushion 30 may not be attached to the back rest 22, but may instead be positioned between the user and the back rest 22. Alternatively, the cushion 30 may be either permanently or removably attached to the back rest 22 or any other acceptable part of wheelchair 10 using clips, snaps, hook and loop fasteners, ties, or any other acceptable attachment device or method, or combination of attachment devices and methods.

In one embodiment, back rest cushion 30 includes a cover 60 and a cushion member 38. The cover 60 is designed to enclose and protect the cushion member 38, and to interface with that portion of the wheelchair user's body which contacts the back rest cushion 30. The cover 60 includes an access 62, which allows the cushion member 38 to be placed inside of or removed from the cover 60. Access 62 may include a zipper (not shown) which can be used to close the access once the cushion member is enclosed within the cover 60. The area around the access may be constructed from similar materials as those used to construct the interface member 36 or backing 40. Alternatively, any suitable materials may be used, including any nylon or similar materials.

Cover 60 includes an interface member 36, which extends over most or all of the front surface 31 of the cover 60. In addition, interface member 36 may extend over parts or all of the edge surface 35 and the back surface 33. Alternatively, cover 60 may include a backing 40, which forms at least a part of the back surface 33 of cover 60, although it may be adjacent any surface or combination of surfaces. Backing 40 is constructed of a nylon mesh material with a mesh pattern large enough to provide for adequate air and moisture transfer. If the cover 60 includes backing 40, backing 40 is attached to interface member 36 by a suitable structure such as stitching (not shown). Alternatively, backing 40 may be attached to interface member 36 via snaps, buttons, adhesives or any other suitable mechanism. It is to be understood that while the interface member 36 and backing 40 are described as being attached to form a cover 60, it is possible that the interface member 36 is not directly attached the backing 40, but that the interface member 36 may be attached to the cushion member 38.

Interface member 36 may be constructed of a multi-layered material such as Dri-lex® lining material manufactured by Faytex Corporation. This material includes a hydrophobic outer layer 42, located on at least part of the exterior surface of the interface member 36. The outer layer 42 can be constructed of a variety of hydrophobic polymer materials such as a woven polypropylene or other acceptable material, and is constructed so that it has a mesh pattern or other suitable configuration with enough vacancies within the outer layer 42 to allow moisture and air to travel freely through it. The outer layer 42 has a thickness of approximately one millimeter, although that thickness may vary substantially and may be non-uniform across the surface of the outer layer. In addition, the interface member 36 may also include an inner layer 46.

The inner layer 46 is constructed of an hydrophilic material such as Hydrofil® Nylon, manufactured by Honeywell, Inc., although any suitable hydrophilic material may be used. Inner layer 46 has a mesh-type pattern that allows air and water to pass freely through it. Inner layer 46 is approximately the same size and shape as the outer layer 42 and is positioned substantially parallel to the outer layer 42. In one embodiment, the inner layer 46 has a relatively uniform thickness—usually less than one millimeter. Alternatively, the inner layer 46 may vary in thickness in a similar fashion as the outer layer 42.

Interface member 36 may also include a spacer layer 44 located between the outer layer 42 and the inner layer 46. The spacer layer 44, in one embodiment, is constructed of a hydrophobic material, although any suitable material may be used. Spacer layer 44 is positioned so that its fibers are generally perpendicular, that is, within about 45 degrees of perpendicular, to both the outer layer 42 and the inner layer 46. The spacer layer 44 has a thickness of about six millimeters, although that thickness may vary substantially in alternative embodiments. Further, the thickness of spacer layer 44 may or may not be uniform across the interface member 36. The perpendicularity and the hydrophobic nature of the fibers that make up the spacer layer 44 allow moisture to move freely from the hydrophobic layer 42 to the hydrophilic layer 46. Further, the spacer layer 44 provides a cushioning effect which aids in the distribution and minimization of contact pressure on that portion of the wheelchair user's body which contacts the back rest cushion 30.

Spacer layer 44 is woven to both the outer layer 42 and the inner layer 46 so that the three layers are attached to each other and substantially form the interface member 36. It is to be understood, however, that the spacer layer 44 may alternatively be attached to the outer layer 42, the inner layer 46, or both by using an adhesive, heat bonding, or any other suitable attachment device or process. It is to be further understood, that the spacer material may simply be positioned between the outer layer 42 and the inner layer 46 without actually being attached to either layer.

In one embodiment, interface member 36 has a varying thickness. For example, the thickness of interface member 36 may vary across the front surface 31 of cover 60 to provide more cushioning in specific areas for the wheelchair user's body. Alternatively, the interface member 36 may have a differing thickness on differing surfaces of cover 60, if it should form other surfaces of cover 60. For example, interface member 36 may be generally thicker on the front surface 31 than it is the edge surface 35 and/or the back surface 33.

Cushion member 38 includes a cushion portion 37, constructed out of a breathable material that provides cushioning and is sufficiently permeable to allow moisture and air to flow freely through it. In one embodiment, the cushion portion 37 is constructed of spherical particles of closed cell foam, approximately 0.25 inches in diameter. These particles are packed together and are attached, adhered, bonded, or otherwise connected together at their tangent points or surfaces, leaving vacancies between the particles that allow air and moisture to flow through the foam in all directions. An example of such a foam is Brock® foam, manufactured by Brock USA.

While the particles in one embodiment are spherical in shape, alternatively they may be of any particular shape that allows for vacancies between particles when closely concentrated together. For example, a particle may have a regular shape, such as a dodecahedron or a icosahedron, or it may have any irregular shape that provides such vacancies when the particles are connected to each other at their tangent points or surfaces. While in one embodiment particles have a diameter of approximately 0.25 inches, any particle size, larger or smaller, which will allow for sufficient vacancies between the particles when they attached to one another is acceptable. In addition, the particles may be of varying, non-uniform sizes.

Referring to FIG. 5, cushion member 38 has a generally rectangular, three-dimensional shape, although alternatively, the shape of cushion member 38 may vary. For example, a front surface 50 of cushion member 38 may have concave curvature (not shown) or have multiple angles to approximate a concave surface so as to conform at least partially to a portion of the user's body. Alternatively, the front surface 50 may be non-planar with respect to its opposing surface over some or all of its surface to provide support for various parts of the user's body. In addition, the cushion member 38 may have rounded and/or tapered corners or be irregularly shaped as shown in FIG. 5.

While cushion member 38 may consist solely of cushion portion 37, it may also include other elements. For example, cushion member 38 may include a support member 39 as shown in FIG. 4. Support member 39 may be positioned along a substantial portion of the cushion member 38. Support member 39 may be constructed of an air and moisture permeable material similar in properties to those of cushion portion 37. Alternatively, support member 39 may be constructed of any polymeric, metallic or other acceptable material that does not have substantial permeability. In such an instance, support member 39 are formed to include at least one vacancy 41 so that air and moisture may move through the cushion member 38. It is to be understood that support member 39 may be more rigid than cushion portion 37 to provide improved support for the user's body, or less rigid to provide increased cushioning for part of the user's body. Support member 39 may be positioned along or attached to a single surface of cushion portion 37. If support member 39 is attached to cushion portion 37, it may be attached through the use of an adhesive, attachment devices integrated into support member 39, interlocking attachment mechanisms integrated into both cushion portion 37 and support member 39, or any attachment mechanism including clips, screws, or other acceptable fasteners.

While support member 39 is shown to be a single structure attached to a back surface of cushion portion 37, support member 39 may be located anywhere with respect to cushion portion 37 including being integrated with cushion portion 37. Further, support member 39 may include multiple structures of the same or varying shapes and materials, which may be located anywhere on or within cushion portion 37, including on any surface or combination of all or part of the surfaces of cushion portion 37.

The back rest cushion 30, with its collection of components designed to encourage air flow and moisture evacuation away from the user's skin, provides a significant improvement in those areas over the state-of-the-art cushion. However, the cushion of the preferred embodiment, with its interface member 36 and cushion member 38 each providing cushioning, has been shown to provide surprisingly better minimization and distribution of pressure in a pressure mapping test conducted against a state-of-the-art “Back 1” back rest cushion manufactured by Otto Bock, Inc. (part number 476D10=RA15-17).

The pressure mapping test was conducted by using pressure sensors placed in a grid along the back rest cushion to determine the cushions' performance as determined by three parameters: contact surface area, peak pressure and pressure dispersion. The wheelchair was then positioned at various inclined positions and pressure measurements were taken to calculate the three parameters.

The back rest cushion 30 showed consistently higher contact surface area performance than the Back 1 cushion. A higher contact surface area is desirable, as a larger contact area indicates that contact pressures are less likely to be concentrated in certain areas. The average reading at different angles of incline showed about an 8% increase in contact area.

Likewise, the back rest cushion 30 of the present invention showed improvements in its peak pressure and pressure dispersion readings. On average, the cushion 30 of the present invention had about 3% lower peak pressure on the cushion 30 at different incline angles and about 7.25% better pressure dispersion than was found with the Back 1 cushion. Therefore, the cushion 30 of the present invention reduces the contact pressure and provides improved pressure distribution across the contact surface than the state-of-the-art cushion.

While the details of the invention have been described with respect to the back rest cushion 30, it is to be understood that the invention may be adapted to the other cushions such as the head rest cushion 34 or the arm rest cushion 32 that may be incorporated in a wheel chair. While the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. 

1. A cushion adapted to reduce heat and moisture from a wheelchair user's body, comprising: a cushion member including a compressible material that permits air and moisture to flow through the cushion member; and an air and water permeable cover adapted to receive the cushion member, the cover including an interface member having: an outer layer formed of a hydrophobic material; an inner layer formed of a hydrophilic material and positioned substantially parallel to the outer layer; and a spacer layer constructed of a compressible hydrophobic material and having fibers positioned between, and generally perpendicular to, the outer and inner layers.
 2. The cushion of claim 1, wherein the interface member has a varying thickness.
 3. The cushion of claim 1, wherein the cushion member has a varying thickness.
 4. The cushion of claim 1, further comprising a support member, wherein the support member is more rigid than the cushion member and cover, to provide stability for a wheelchair user.
 5. The cushion of claim 4, wherein the support member includes an aperture to allow air and moisture to flow through the support member.
 6. The cushion of claim 4, wherein at least a portion of the support and cushion members have complementary shapes.
 7. The cushion of claim 1, wherein the spacer layer is attached to the outer layer.
 8. The cushion of claim 1, wherein the spacer layer is attached to the inner layer.
 9. The cushion of claim 1, wherein the cover further includes an air and moisture permeable backing member attached to the interface member.
 10. The cushion of claim 1, wherein the cushion is configured to interface with at least one of the wheelchair user's back, arm, head, and leg.
 11. The cushion of claim 1, wherein at least one major surface of the cushion is non-planar.
 12. A wheelchair, comprising: a frame; at least two wheels attached to the frame; a seat attached to the frame; and a cushion, positioned with respect to the frame so as to be adjacent to a portion of a wheelchair user's body when the user is sitting in the wheelchair, the cushion including: a cushion member including a compressible material that permits air and moisture flow through the cushion member; and an air and water permeable cover adapted to receive the cushion member and having an air and water permeable interface member.
 13. The wheelchair of claim 12, wherein the interface member includes: an outer layer formed of a hydrophobic material and extending along at least a substantial portion of a surface of the cover positioned adjacent to the user's body; an inner layer formed of a hydrophilic material and positioned substantially parallel to the outer layer; and a spacer layer constructed of a compressible hydrophobic material and having fibers positioned between, and generally perpendicular to, the outer and inner layers.
 14. The wheelchair of claim 12, further comprising a support member that is attached to the cushion, wherein the support member is more rigid than the cushion member and cover.
 15. The wheelchair of claim 12, wherein the cushion is configured to interface with at least one of the wheelchair user's back, arm, head, and leg.
 16. A method for reducing heat and moisture from a body surface of a wheelchair user seated in a wheelchair, comprising: providing an air and moisture permeable cushion including: a cushion member having a compressible material that permits air and moisture to flow through the cushion member; and a cover adapted to receive the cushion member and engage a portion of the wheelchair user's body; and positioning the cushion between a portion of the wheelchair user's body and the wheelchair.
 17. The method of claim 16, wherein providing the cushion further comprises providing an interface member for the portion of the cover engaging a portion of the wheelchair user's body, the interface member having: an outer layer formed of a hydrophobic material; an inner layer formed of a hydrophilic material and positioned substantially parallel to the outer layer; and a spacer layer constructed of a compressible hydrophobic material and having fibers positioned between, and generally perpendicular to, the outer and inner layers.
 18. The method of claim 17, wherein providing the cover further comprises attaching the spacer layer to the inner layer and outer layer.
 19. The method of claim 16, wherein positioning the cushion includes positioning the cushion between the wheelchair user's back and the wheelchair.
 20. The method of claim 16, wherein positioning the cushion includes positioning the cushion between at least one of the wheelchair user's arm, leg or head and the wheelchair. 